It's an annual event, which lasts for two weeks. This year's school is on right now. All the PhD students in experimental particle physics in the UK go to it at the end of the first year of their PhD studies, and they learn. We are a fairly multinational bunch, though UK dominated of course, and you aways remember who was on that two-week school with you. It's your school year. I learned how to calculate the Higgs production cross section in electron-positron collisions from first principles, and forgot it again very quickly, but it is good to know that I knew once. I also learned how to not to play ultimate frisby, though maybe more accurately I learned who not to play it with. Also, don't cross your legs on group photos, it makes you look like a dork.

Ten years ago this week I was a tutor at the Rutherford Summer School.

I came downstairs on the Tuesday to lead a tutorial and found everyone clustered around the TV watching the twin towers burn. The husband of a friend and colleague was working in one of the smaller buildings next to them (he's ok). My wife, who was expecting our first child, was working in the City of London. I phoned and found out she had stayed home with morning sickness - I have never been so glad to hear she was ill.

We picked up the physics the following day, pretty much, in a subdued and sightly stunned way, with half an eye on the news.

I don't have anything to add really to the commentary on those events. Pretty much everything I'd want to say has been said by people either more involved or more eloquent or both. But this weekend it's on my mind and it seemed appropriate to mention it at least.

I have been thinking about terrorism more generally too. I think even as the perpetrators succeed in killing and maiming innocent people, the activity loses its power to change much, except for those directly involved.

I went to Mumbai recently, and swam in the pool at the Taj Mahal, the hotel which was attacked in 2008 by gunmen for reasons which presumably made sense to them at the time. A few weeks before I went, there was a terrorist bombing in Mumbai. But I didn't consider changing my travel plans. Why would I? I went to New York last year. In 2005 you could hear a London bus blow up from my office. In the end, terrorism isn't modifying my behaviour because it could happen pretty much anywhere, and the chances are low enough that it's best just to ignore it when it comes to planning your life. There have always been barbarians.